Recently, some of portable information terminals such as mobile phones and PDAs (Personal Digital Assistants) are designed such that a display section can display graphics, and GUI (Graphical User Interface) which uses the display section in two-dimension is employed as a method for displaying information to users. However, as the portable information terminals have higher performances and become closer to display performances of computers, there arises a problem that the portable information terminals require complicate operations.
In general, the portable information terminals employ a keypad as a user interface via which information is entered. A keypad consists of a plurality of keys via which numerals and characters are entered, and direction keys. However, under the aforementioned circumstance in which the portable information terminals require complicated operations, an input using menu keys and other function keys of a keypad as direction keys is not suitable for selection of icons displayed by a GUI, and consequently a desired operation cannot be performed easily. Therefore, it is difficult to employ the input using the keypad as direction keys for the portable information terminals. Accordingly, the portable information terminals are required to mount pointing devices having the same operativity as those of mice and touch pads used for computers.
Under such circumstance, as pointing devices that can be mounted on portable information terminals, there has been proposed a pointing device which observes, by an imaging element, a pattern of an object such as a fingertip touching the pointing device and detects the change in the pattern of the object on the touching interface, so as to detect the movement of the object. Further, there has been proposed a pointing device which irradiates a touching interface with a light source, causes a pattern of an object on the touching interface to be focused on an imaging element via a lens, and detects a change in the pattern, so as to convert the movement of the object into an input signal and detect the movement.
Conventional examples of such pointing devices include pointing devices disclosed in Patent Literatures 1 and 2 below.
The pointing device disclosed in Patent Literature 1 includes a cover glass, a light source section, and a light receiving section. The light source section includes a light source and a light source guide consisting of a plurality of reflecting mirrors provided above the light source. Light emitted from the light source is reflected by a reflecting mirror by a predetermined angle, and is incident to the cover glass. The light incident to the cover glass is reflected by a surface of a finger, and the light reflected by the surface of the finger is incident to the light receiving section. The light receiving section includes a reflecting mirror, a condensing lens, and a light image sensor. The light incident to the light receiving section is reflected by the reflective mirror, imaged by the condensing lens, and is incident to the light image sensor.
The pointing device disclosed in Patent Literature 2 includes a light source for irradiating an object with light, a collimating lens for subduing diffusion of the light from the light source, a reflective surface for reflecting the light from the collimating lens by a predetermined angle so that the reflected light goes toward an image acquiring surface, the image acquiring surface, an imaging element for condensing an image from the image acquiring surface, and a light sensor for receiving the condensed image and converting it to an electric signal.